Miniaturization of device structure is advanced with enhanced performance of semiconductor devices. Width of wiring in a device becomes fine, and aluminum conventionally used as a wiring material gives rise a problem in delay of signal transmission. As a result, copper has been used. Copper has the characteristic that resistance is low, but has the disadvantage that it is liable to be diffused in a silicon oxide used in an insulating film between wirings, resulting in degradation of performance of the insulating film. For this reason, a method is employed that a barrier film for preventing the diffusion is provided between the wiring and the insulating film. As the barrier film, a tantalum nitride film is generally used from high ability of preventing diffusion of copper. However, the tantalum nitride film has poor adhesion to a copper seed film for forming a copper wiring by plating, and film peeling occurs between the tantalum nitride film and the copper seed film when forming a wiring or planarizing after wiring formation, resulting in generation of defect. For this reason, a method is employed that a metallic tantalum film is formed between the tantalum nitride film as a barrier film and the copper seed film, thereby preventing the film peeling.
At present, a tantalum nitride film and a metallic tantalum film are mainly formed by a physical vapor deposition method (PVD method) by sputtering. In the PVD method, it is difficult to form a uniform film on a concave-convex surface, and from now, where miniaturization of a semiconductor device is advanced, it will be required to form a uniform and thin film on a surface of a complicated three dimensional structure. Because of this, investigation is made in formation by a chemical vapor deposition method (CVD method) that decomposes raw material gases of a metal halide, an amide compound, an organic metal compound and the like to deposit a film, or by an atomic layer deposition method (ALD method) that decomposes those raw materials adsorbed on a substrate surface to deposit a film.
When a tantalum nitride film or a metallic tantalum film is formed by CVD method or ALD method, it is desirable that both films can be formed from the same tantalum raw material in one reaction chamber. As a raw material of such a formation method, a halide such as TaCl5 and TaBr5 is investigated (for example, see Non-Patent Document 1). Further, as a raw material of a tantalum nitride film, an amide compound such as Ta(NMe2)5, Ta(NEt2)5 (for example, see Non-Patent Document 2) and tBuN═Ta(NEt2)3 (for example, see Non-Patent Document 3) is investigated. However, the halide has high melting point and is required to vaporize by sublimation. Thus, it is difficult to use the halide as a raw material in CVD method or ALD method. Additionally, there are the problems on corrosion of a film due to a residual halogen in a film, deterioration of adhesion and the like. On the other hand, in the amide compound, because nitrogen remains in a film, it is possible to form a tantalum nitride film, but it is difficult to form a metallic tantalum film. For this reason, a tantalum raw material for CVD or ALD that does not contain a halogen and nitrogen in the molecule is required, and a method of using an organometallic compound such as ((Si(CH3)3)C5H4)Ta(CO)4 (see Patent Document 1) or ((Si(CH3)3)C5H4)2TaH3 (see Patent Document 2) is investigated. However, there are the problems that those tantalum compounds have low heat stability, and are difficult to vaporize stably.
Cp2TaH3 (see Non-Patent Document 4) and Cp2Ta(CO)H (see Non-Patent Document 5) are known a tantalum-containing organometallic compound.
Patent Document 1: U.S. Pat. No. 6,491,987
Patent Document 2: U.S. Pat. No. 6,743,473
Non-Patent Document 1: X. Chen, H. L. Frisch, A. E. Kaloyeros, B. Arkles and J. Sullivan, J. Vac. Sci. Technol. B 1999, 17, 182
Non-Patent Document 2: K. Sugiyama, S. Pac, Y. Takahashi and S. Motojima, J. Electrochem. Soc. 1975, 122, 1545
Non-Patent Document 3: M. H. Tsai, S. C. Sun, C. E. Tsai, S. H. Chuang and H. T. Chiu, J. Appl. Phys. 1996, 79, 6932
Non-Patent Document 4: M. L. H. Green, J. A. McCleverty, L. Pratt and G. Wilkinson, J. Chem. Soc. 1961, 4854
Non-Patent Document 5: A. H. Klazing and J. H. Teuben, J. Organomet. Chem. 1978, 157, 413